1. Field of the Invention
This invention relates to a data multiplexing method for allowing video data, audio data and metadata to be reproduced synchronously and an apparatus for the same, and a data demultiplexing method and apparatus.
2. Description of the Related Art
As for a method for multiplexing elementary data series of video data, audio data and metadata to reproduce them synchronously, MPEG-2 Systems (ISO/IEC13818-1) are laid down as an international standard (ITU-T Rec.H.222.0 (2000)|IS0/IEC 13818-1:2000 (MPEG-2 Systems)). The original MPEG-2 Systems standard establishes a mechanism of multiplexing video code data, which is encoded by an MPEG standard family video encoding scheme such as MPEG-1, MPEG-2 or MPEG-4, audio code data and the data which a user defined privately. Thereafter, the MPEG-2 Systems standard established expansion of a standard to support multiplexing of the metadata (ITU-TRec.H.222.0 (2000)/Amd.2 (06/2003)|ISO/IEC13818-1:2000/Amd.2:2004).
The MPEG-2 Systems standard defines two types of multiplexing formats of a transport stream (TS) and a program stream (PS). TS is a format utilized by broadcast, and a program stream is utilized in DVD. The program stream is formed in unit called a plurality of packs. The pack is formed of one pack header and 0 or more PES (Packeted Elementary Stream) packets. The pack header is formed of one main pack header and 0 or 1 system header, and includes information of a time at which the pack is received. The PES packet is formed of one PES header and a PES payload of 0 or more bytes. The elementary stream such as video data, audio data and metadata is divided in a suitable size and stored in the PES payload. The stream ID that is an identifier for classifying data included in the PES payload is recorded in the PES header, and one continuous elementary stream can be derived from the divided elementary streams by coupling PES payloads of the same stream ID. Further, when the data included in the PES payload includes a boundary of a picture of video or a frame of audio, the time at which a next picture or a next frame is reproduced and displayed may be recorded in the PES header in a form of a relative time from a receipt time of the pack indicated by receipt time information in the pack header.
A system header includes information on a systematic feature of the program stream. For example, buffer size information necessary for generating and reproducing an elementary stream of a stream ID is recorded in a form of a pair of the stream ID and buffer size.
In extension of a MPEG-2 Systems standard for meta data multiplexing, which is disclosed in ITU-TRec.H222.0 (2000)/Amd2 (06/2003)|ISO/IEC13818-1:2000/Amd2:2004, a value such as extension ID (extended_stream_id=0xFD) is newly defined to the stream ID for use in the PES header so that plural meta data can be identified. In the case of extension ID, 128 kinds of elementary streams can be identified using a value of 7 bits as referred to as an extension stream ID (stream_id_extension).
However, in extension of MPEG-2 Systems by a technique disclosed in ITU-TRec.H.222.0 (2000)/Amd.2 (06/2003)|ISO/IEC13818-1:2000/Amd2:2004, a recording scheme for buffer size information (extension buffer size information) for every extension stream ID is not extended nor provided in system header. Therefore, only recording the buffer size information commonly on the extension ID is possible as it is, and an additional extension of the standard is desired in order to provide a scheme for recording the extension buffer size information for every extension stream ID.
Products using the extension disclosed in ITU-TRec.H.222.0 (2000)/Amd.2 (06/2003)|ISO/IEC13818-1:2000/Amd.2.2004 have already been released in the market. Accordingly, when additional extension of the standard is done, it is desired in industry to have “back word compatibility” for the purpose of avoiding confusion in the market. Further, it is desirable to ensure “forward compatibility” that allows data (a program stream) created according to an existing standard to be normally reproduced even by equipment developed according to the additional extension standard.
It is an object of the present invention to provide a data multiplexing/demultiplexing method and an apparatus for the same which can record extension buffer size information for each extension stream ID without generating an error at the time of playback by use of conventional equipment and at the time of playback of conventional data by use of new equipment.